Holiday reunions are meant to be pleasurable, but in Danny Reagan's case, it's not exactly a shock such an encounter would keep him on the job.

The NYPD detective (
Donnie Wahlberg) initially enjoyed welcoming his childhood friend Mickey (guest star
Tom Cavanagh) back home in "Ties That Bind," the last 2013 episode of CBS'
"Blue Bloods." In the tale by series co-executive producer
Brian Burns, Mickey and wife Connie (guest star
Rebecca Budig) relocated from Florida back to New York to help care for her ill mother.

Looking out his window and admiring Mickey's Mercedes, Danny also saw a supposed electric-company van he immediately "made" as a surveillance vehicle. At work the next day, Danny was shown photos by the detective who conducted the stakeout -- and who inferred that presumed Realtor Mickey actually was connected to one of Florida's top crime families.

Frank (
Tom Selleck) paid a hospital visit to an officer wounded in the line of duty, and the cop's partner indicated he'd hesitated to question one of the perpetrators earlier because of new frisking restrictions. The partner had feared being on the receiving end of a personal lawsuit if his hunch about the suspect having a weapon was wrong.

Told Mickey was a go-between for mobsters, Danny replied that if that were true, "He deserves whatever he's got coming." It didn't end there: The lead investigator wanted Danny's help in exposing Mickey, reasoning that "if we flip him, we just took down the biggest mob operation in 20 years." Danny refused, saying it also would mean "I will have sold my soul," but he was warned his cooperation could be demanded rather than requested.

Erin (
Bridget Moynahan) told Danny she knew Mickey had been trouble when the two were kids, but Danny felt beholden because Mickey had taken a shoplifting rap for them both. Erin told her brother that before doing anything, he should make sure Mickey really was involved in criminal activities.

Danny's agent of discovery was Maria (
Marisa Ramirez), who covertly tailed Mickey to an office building -- and helped trace him to a business that was a front for a crime family. Danny then agreed to help in a sting if Mickey would be offered witness protection. For having been wrong, Danny invited the accusing detective several times to punch him, and the other investigator finally did.

There was a reason: While playing darts at a bar later, Danny told Mickey he'd gotten his black eye from being in debt over gambling on horse races. He upped the story by claiming he was behind on car payments and his sons' tuition, prompting Mickey to offer to help him out.

Danny resisted by saying, "You and I both know what money does to friendships." Mickey then said, "I might know a guy that might be able to give you some work. But no promises. And no more betting."

Frank met with Mayor Poole (
David Ramsey) about the new frisking dictates, explaining, "We'd like some help." That meant the mayor reinforcing to the public that their assistance was needed in spotting and stopping crimes. "Let me think about it," said the mayor, himself a victim of crime as his wheelchair confirmed.

Danny and Linda (
Amy Carlson) dined out with Mickey and Connie, and when the women left the table, Mickey tried to rescind his offer to help Danny find a certain kind of extra work. Danny pressed him on what kind of work it would be: "Just introduce me to the guy. Let me figure it out for myself."

As the meeting approached, Danny didn't want to wear a wire, but finally agreed to. He arrived at a church where Mickey, the only other person present, wanted to pat him down before they talked business. "No offense," Mickey said, "you are a cop. I'd be stupid not to take precautions." He proceeded to, and he detected no wire.

Danny had taken it off before he entered the church, and Mickey then said "enough to incriminate himself," as Danny reported back -- but without recorded proof, that wasn't good enough. However, Danny again proved his resourcefulness, having stashed a second phone in his sock to capture Mickey's voice.

Three generations of Reagans debated the frisking law at home, with Henry (
Len Cariou) saying cops should proceed and risk it, while Jamie (
Will Estes) worried about possible lawsuits. Frank again stressed his officers had to "live with it." However, Jamie's expression of his experiences made Frank realize "this falls on my shoulders."

Danny went to Mickey and told him about the recording he'd made, leading an incredulous Mickey to ask, "You framed me? Your oldest friend, and you set me up?" Instead of letting Danny arrest him, he threw the first punch ... starting a literal knock-down, drag-out fight.

Danny got the upper hand and took Mickey in for interrogation, where the latter insisted, "I put people together, I buy and sell companies, I move some money around and that's it. I've got nothing to do with anybody getting hurt." Danny replied that even if Mickey himself didn't cause hurt, his associates did, "which makes you just as guilty."

By the time the ambitious Mickey had realized what he was involved in, as he explained, "It was too late." Maybe not, Danny suggested, recommending Mickey testify against "these animals." Mickey didn't want his family to have to give up the lives they knew, though, and his lawyer then entered to remove him from the interrogation room.

It didn't take long for Mickey's crime-family peers to order a hit on him, and even with him being in police custody, Danny was worried. He had good reason: Just as Henry was trying to make him feel better about what he'd done regarding Mickey, Danny got a call that Mickey had made bail ... posted by "a soldier" of the crime family.

Frank brought the mayor along on a stakeout, sizing up a young man who apparently was concealing a weapon. "If he's carrying a gun, someone needs to stop him," the mayor said. "What if I'm wrong?" Frank asked, and the mayor recognized the "lesson" he was being taught.

Desperate to find Mickey, Danny went to Connie, who showed him a cell-phone message with a certain code Danny knew from childhood. He was able to decipher it meant Mickey was being taken to be eliminated; Danny determined where and went there, and a shootout with Mickey's would-be killers ensued.

Counting the number of shots fired, Danny knew when the gunman had spent his bullets and took him out, then went to stop the other mobster from choking Mickey to death. "This is what's gonna happen," Danny told Mickey afterward. 'You're gonna make a change, you're gonna set things right, and then -- maybe then -- I'll consider calling you a friend again."

Mickey agreed to testify against the crime family, and Danny said he'd be there for it. "'Thank you doesn't seem like enough," Mickey told him. "It's not enough," Danny confirmed.

Frank addressed many of his officers the next day, reasserting the new frisking limits had to be obeyed, regardless of the cops' opinions of them. At the same time, he stated the stop-and-frisk procedure was "not something we are discarding altogether. And I can tell you that the mayor 'gets' that."

Adding that he would provide "clear guidelines," Frank ended by telling his cops, "I will, always, have your back."

Then it was dinner time for the Reagans, where they invoked Mickey's name in mulling how anyone could know what sort of person someone would turn out to be. Frank used the seasonal example of Ebenezer Scrooge as somebody who can change.

Smiling, he then confirmed that an envelope of cash Danny was handed on his 21st birthday had been a "bail fund" his mother had stored away, in case it ever had been needed during his adventuresome youth ... to the amusement of others at the table, and even to Danny.